The subject matter of the present invention is a shielded, air-tight enclosure equipped so as to be usable in emission spectrometry.
The emission spectrometry method of analysis, with its traditional arc-spark sources, has been known for several decades.
At the present time a new source, called an "inductive coupling plasma" (ICP) is being used in many laboratories.
In these known apparatus a high-frequency power source supplies electrical energy to a hollow cylindrical inductor made by winding successive turns of hollow copper tubing inside of which cooling water circulates.
The solution containing the chemical elements to be analyzed is vehicled in the form of a fog by a current of inert gas, such as argon, circulating axially within the coil of the inductor, such that the powers, raised to a sufficient frequency, dissipated by this inductor create in an axial zone of this inductor a high-temperature plasma.
A spectrometer, centered on this plasma, makes it possible to determine and quantify the different cations present in the solution by studying the emission spectrum.
This method permits the analysis of the cations within detection limits close to a microgram per liter, allowing very great dilutions of the elements to be analyzed in the solution.
Furthermore, this method of analysis involves but a very small consumption of the solution, of the order of 5 milliliters per hour, when the fog is produced by ultrasound.
Another advantage of this method is the speed of the analysis, which is performed in about one minute per element metered.
Lastly, the precision obtained, of the order of 1%, is decidedly improved in comparison with other usable arc or spark sources of plasma.
These advantages of this method of analysis are of very particular interest for reasons of nuclear safety, when it is desired to analyze radioactive elements of fission products, because naught but extremely small quantities of these elements are used.
Nevertheless, it is necessary to perform the analysis in a shielded, air-tight enclosure.
The present invention is more precisely related to the equipment of an air-tight enclosure permitting the application of the emission spectrometry analysis method set forth above, to radioactive chemical elements in solution.
As it is well known in nuclear technology, when an apparatus that is to be operated in a shielded enclosure is designed, the effort is made to put only a minimum of parts, devices or equipment of the apparatus within this enclosure, and to construct these different components so that they will be as simple as possible so as to be easily handled by means of telemanipulators, and so that their reliability and useful life will be as great as possible.
In the case of the emission spectrometry apparatus concerned by the invention, the general thrust of the design of the apparatus was therefore to house within the shielded enclosure only the active part in contact with radioactive elements, that is to say, the inductively coupled plasma source, and to locate outside of the shielded enclosure the high-frequency generator, on the one hand, and the spectrometer on the other.
To do this it was necessary first of all to remove this plasma source physically away from the high-frequency generator by a distance of several tens of centimeters and to connect them through the shielded wall of the enclosure.
This first problem was solved by a first invention of the same inventors, which is the subject matter of French Patent Publication No. 2564233 entitled, "Improved inductor for a plasma source, usable in emission spectrometry."
This inductor is characterized in that it includes two powersupply conductors of a length between 20 and 40 cm, constituted by two hollow, stainless steel tubes connected at one of their ends to coils made of a hollow, stainless steel tube, their other ends to be connected electrically to a high-frequency generator, and means being provided for circulating cooling air within the said connected hollow tubes.
It is the purpose of the present invention to provide an apparatus for the equipment of an air-tight enclosure adapted to this type of inductors and to the general configuration of emission spectrometry apparatus, mentioned above.